1. Field of the Invention
The present invention relates to an image forming apparatus and method of forming images on both sides of a recording medium.
2. Discussion of the Background
Image forming apparatuses, such as printers, copying machines, facsimile machines, etc. which form images on both sides of a recording medium (hereinafter may be referred to as a sheet) are known.
Such image forming apparatuses capable of forming images on both sides of a sheet generally transfer an image of one side of an original, which has been formed and visualized on an image bearing member, onto one side of a sheet, and then fix the image onto the sheet by a fixing device. The sheet is then reversed by a reversing path, etc., and is conveyed again so that an image of the other side of the original, which has been also formed and visualized on the image bearing member, is transferred and fixed onto the other side of the sheet.
In the above image forming apparatuses, because a sheet conveying direction has to be reversed, and a sheet tends to be curled when an image is fixed onto one side of the sheet, reliability of sheets conveyance is hard to be obtained.
Japanese Laid-open Patent Publications No. 1-209470 and No. 11-327335 respectively describe an image forming apparatus in which toner images, which have been transferred onto both sides of a sheet from a first image bearing member and a second image bearing member, are fixed at one time.
Japanese Laid-open Patent Publication No. 1-209470 describes an image forming apparatus that transfers a first image formed on a photoreceptor onto a transfer belt by a first transfer device and then transfers a second image formed on the photoreceptor onto one side of a sheet by the first transfer device. Thereafter, the image forming apparatus transfers the first image on the transfer belt onto the other side of the sheet by a second transfer device, thus transferring the images on both sides of the sheet. The sheet is then conveyed to a fixing device, where the images are fixed onto both sides of the sheet.
Japanese Laid-open Patent Publication No. 11-327335 describes another image forming apparatus that includes two transfer devices. After transferring multi-color images onto both sides of a sheet, the sheet is conveyed to a fixing device, and the images are fixed onto both sides of the sheet at one time by the fixing device. The image forming apparatus further includes a spur having plural protrusions on its circumferential surface so as to guide conveyance of a sheet having unfixed multi-color images on both sides thereof.
According to one aspect of the present invention, an image forming apparatus which may form first and second visual images on first and second sides of a recording medium, includes a first image bearing member configured to bear the first and second visual images, a second image bearing member configured to bear the first visual image transferred from the first image bearing member, a first transfer device configured to transfer the first visual image formed on the first image bearing member onto the second image bearing member or the second visual image formed on the first image bearing member onto the second side of the recording medium, a second transfer device configured to transfer the first visual image carried by the second image bearing member onto the first side of the recording medium, and a fixing device configured to fix the first and second visual images transferred onto the recording medium. The fixing device includes first and second fixing members so as to fix the second and first visual images on the second and first sides of the recording medium, respectively. The first fixing member and the second image bearing member contact the second and first sides of the recording medium, respectively, and surface properties of the first fixing member and the second image bearing member are substantially the same.
According to another aspect of the present invention, an image forming apparatus which may form first and second visual images on first and second sides of a recording medium, includes a first image bearing member configured to bear the first and second visual images, a second image bearing member configured to bear the first visual image transferred from the first image bearing member, a first transfer device configured to transfer the first visual image formed on the first image bearing member onto the second image bearing member or the second visual image formed on the first image bearing member onto the second side of the recording medium, a second transfer device configured to transfer the first visual image carried by the second image bearing member onto the first side of the recording medium, and a fixing device configured to fix the first and second visual images transferred onto the recording medium. The fixing device includes first and second fixing members so as to fix the second and first visual images on the second and first sides of the recording medium, respectively. The first and second fixing members contact the second and first sides of the recording medium, respectively, and surface properties of the first and second fixing members are substantially the same.
According to still another aspect of the present invention, a method of forming an image, includes transferring a first visual image formed on a first image bearing member onto a second image bearing member, transferring a second visual image formed on the first image bearing member onto a second side of a recording medium, transferring the first visual image from the second image bearing member onto a first side of the recording medium, bringing a first fixing member and the second image bearing member into contact with the second and first sides of the recording medium, respectively, and fixing the first and second visual images on the first and second sides of the recording medium in a state that surface properties of the first fixing member and the second image bearing member are substantially the same.
According to still another aspect of the present invention, a method of forming an image, includes transferring a first visual image formed on a first image bearing member onto a second image bearing member, transferring a second visual image formed on the first image bearing member onto a second side of a recording medium, transferring the first visual image from the second image bearing member onto a first side of the recording medium, bringing first and second fixing members into contact with the second and first sides of the recording medium, respectively, and fixing the first and second visual images on the first and second sides of the recording medium in a state that surface properties of the first and second fixing members are substantially the same.
Objects, features, and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.